Exhaust system and methods for efficient exhaust heat recovery

ABSTRACT

Systems and methods are described for heating engine coolant by transferring heat from an exhaust flow to the engine coolant via a heat exchanger positioned in an exhaust gas heat recovery line coupled to the EGR cooler responsive to an EGR valve position. In one particular example, a branching pathway of the EGR cooler is positioned downstream of the EGR cooler and allows exhaust gas to be routed to the EGR cooler and/or exhaust gas heat exchanger based on the EGR valve position, which allows for control of the amount of heat transferred to the engine coolant as well as exhaust gas recirculation into the engine. With this arrangement, a cabin temperature of a hybrid vehicle may be increased as quickly as possible under cold start conditions to allow the engine to be quickly turned off after heating the vehicle cabin.

FIELD

The present description relates to an exhaust system and methods forefficiently recovering exhaust heat during vehicle operation.

BACKGROUND AND SUMMARY

Engine systems use several methods to warm up engine coolant duringoperation. For example, FIGS. 1A-C illustrate example schematic exhaustsystems previously implemented. In one example shown in FIG. 1A, theexhaust system includes a cooled EGR arrangement that is used totransfer exhaust heat to the engine coolant. However, a cooled EGR hasthe disadvantage that exhaust heat recovery can only occur when exhaustgas is flowing in the EGR, which limits the amount of exhaust heatrecovery available from the system. Another disadvantage is that exhaustheat recovery is only a portion of the exhaust gas flow, which may be aslow as 25% or lower in some instances relative to the total exhaustflow. Other examples are shown in FIGS. 1B and 1C that include using aseparate exhaust heat recovery heat exchanger and valve assembly,possibly in combination with an EGR cooler. However, while the exhaustheat recovered may be increased compared to FIG. 1A (e.g., via a morefull exhaust heat recovery and independence relative to the EGR flow), aseparate heat exchanger may be large and difficult to package in avehicle. In addition, heat exchangers may be heavy and/or expensive,which increases the cost of the vehicle. Moreover, packaging an exhaustheat recovery heat exchanger separately from the EGR cooler may furtherinclude placing the additional device remotely from the engine, whichreduces the temperature of exhaust gas entering the device duringwarm-up due to heat absorbed by the thermal mass of the upstreamcomponents. This arrangement also has the disadvantage that theavailable heat recovery during engine warm-up is reduced. Yet anotherexample (not shown) includes using a cooled exhaust manifold to extractheat from the exhaust. However, one disadvantage of this arrangement isthat the thermal mass of the exhaust manifold is large, which causes aslow coolant warm-up. Another disadvantage is that both the exhaust gasflow and coolant flow through the exhaust manifold cannot be turned off(e.g., because turning off the coolant flow may cause coolant boiling).Thus, transferring heat from the exhaust to the engine coolant may bemade to occur during certain unfavorable situations in which it ispreferable not to do so, such as at a high temperature and during highload operation.

The inventors have recognized issues with such approaches and hereindescribe a system and methods for heating engine coolant by transferringheat from an exhaust flow to the engine coolant via a heat exchangerpositioned in an exhaust gas heat recovery line coupled to the EGRcooler responsive to an EGR valve position. In particular, an exemplaryEGR cooler combined with an exhaust heat recovery device is presentedthat allows exhaust gas to transfer heat to engine coolant via abranching pathway of the EGR cooler. That is, an exhaust systemconfigured according to the present disclosure allows exhaust gas to berouted to both an EGR and/or the exhaust gas heat exchanger based on EGRvalve actuation. The system further allows for differential actuation ofexhaust flows to distribute the exhaust gasses to both the EGR andexhaust heat exchanger, which enables a differential control of theexhaust flows therein and thereby control of the heat transferred to theengine coolant during operation. In this way, the technical result isachieved that heat can be recovered from the exhaust gas regardless offlow through the EGR line while also allowing for increased heatrecovery from the exhaust gas. One advantage is that up to 100% of theexhaust flow can be allocated to heat recovery based on control of thedifferential flow through the EGHR branch of the exhaust gas heatrecovery device. Another advantage is that the heat recovery can beturned off under operating conditions in which heat recovery may bedetrimental, for example, where maximum cooling is desired. With thisarrangement, the engine coolant may be efficiently and expeditiouslywarmed up, e.g., as quickly as possible, during operation. Furthermore,an exhaust system according to the present disclosure allows for areduced size, weight and cost when implemented into a vehicle.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings. It should be understood that the summary above is provided tointroduce in simplified form a selection of concepts that are furtherdescribed in the detailed description. It is not meant to identify keyor essential features of the claimed subject matter, the scope of whichis defined uniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by readingan example of an embodiment, referred to herein as the DetailedDescription, when taken alone or with reference to the drawings, where:

FIGS. 1A-C illustrate example exhaust systems previously implemented;

FIG. 2 shows an example hybrid vehicle system according to the presentdisclosure;

FIG. 3 illustrates an example EGR cooler coupled to an exhaust gas heatrecovery line according to a first exemplary configuration with an EGHRoutlet connecting to the exhaust passage upstream of a catalyst;

FIG. 4 illustrates a second exemplary configuration with a reduced valveconfiguration;

FIG. 5 illustrates a third exemplary configuration with an EGHR outletline connecting to the exhaust passage downstream of the catalyst;

FIG. 6 illustrates a fourth exemplary configuration where the inlet ofthe EGR cooler couples to the EGHR at a downstream position of the EGHRline;

FIGS. 7 and 8 are example flow charts for switching operational exhaustmodes by adjusting the exhaust flow pathway;

FIG. 9 is an example flow chart for rapidly heating the cabin airtemperature by controlling exhaust flow to the EGHR line according tothe present disclosure; and

FIG. 10 shows an example vehicle operating sequence at engine cold startto illustrate the methods according to the present disclosure.

DETAILED DESCRIPTION

Upon starting a car in cold conditions, passengers may desire expedientcabin warming for a comfortable driving experience. Because cabin air isheated by engine coolant routed to the heater core, heat generated by anengine may be the primary source of heat for the passenger compartmentin some instances. Thus, to reach a threshold cabin temperature abovewhich it is possible to turn off the engine during vehicle operation,for example, to reduce fuel consumption in a hybrid vehicle, the enginemay be operated until sufficient heat has been transferred to the enginecoolant. For this reason, FIG. 2 shows an example hybrid vehicle system.Then, FIGS. 3-6 illustrate exemplary exhaust systems with an EGR coolercoupled to an exhaust gas heat recovery line configured and operatedaccording to the present disclosure. FIGS. 7 and 8 further show examplemethods for changing the operating mode of the vehicle by adjusting anexhaust flow pathway based on valve states whereas FIG. 9 illustratesthe method using an exemplary operating sequence that rapidly heats thecabin air temperature by controlling exhaust flow to the EGHR line. FIG.10 shows an exemplary operating sequence at cold start to illustratevalve adjustments and exhaust flows in greater detail.

Referring now to FIG. 2, a schematic diagram of one cylinder ofmulti-cylinder engine 10, which may be included in a propulsion systemof an automobile, is shown. Engine 10 may be controlled at leastpartially by a control system including controller 12 and by input froma vehicle operator 132 via an input device 130. In this example, inputdevice 130 includes an accelerator pedal and a pedal position sensor 134for generating a proportional pedal position signal PP. Combustionchamber (e.g., cylinder) 30 of engine 10 may include combustion chamberwalls 32 with piston 36 positioned therein. In some embodiments, theface of piston 36 inside cylinder 30 may have a bowl. Piston 36 may becoupled to crankshaft 40 so that reciprocating motion of the piston istranslated into rotational motion of the crankshaft. Crankshaft 40 maybe coupled to at least one drive wheel of a vehicle via an intermediatetransmission system. Further, a starter motor may be coupled tocrankshaft 40 via a flywheel to enable a starting operation of engine10.

Combustion chamber 30 may receive intake air from intake passage 44 viaintake passage 42 and may exhaust combustion gases via exhaust passage48. Intake passage 44 and exhaust passage 48 can selectively communicatewith combustion chamber 30 via respective intake valve 52 and exhaustvalve 54. In some embodiments, combustion chamber 30 may include two ormore intake valves and/or two or more exhaust valves.

In this example, intake valve 52 and exhaust valves 54 may be controlledby cam actuation via respective cam actuation systems 51 and 53. Camactuation systems 51 and 53 may each include one or more cams and mayutilize one or more of cam profile switching (CPS), variable cam timing(VCT), variable valve timing (VVT) and/or variable valve lift (VVL)systems that may be operated by controller 12 to vary valve operation.The position of intake valve 52 and exhaust valve 54 may be determinedby position sensors 55 and 57, respectively. In alternative embodiments,intake valve 52 and/or exhaust valve 54 may be controlled by electricvalve actuation. For example, cylinder 30 may alternatively include anintake valve controlled via electric valve actuation and an exhaustvalve controlled via cam actuation including CPS and/or VCT systems.

Fuel injector 66 is shown coupled directly to combustion chamber 30 forinjecting fuel directly therein in proportion to the pulse width ofsignal FPW received from controller 12 via electronic driver 68. In thismanner, fuel injector 66 provides what is known as direct injection offuel into combustion chamber 30. The fuel injector may be mounted in theside of the combustion chamber or in the top of the combustion chamber,for example. Fuel may be delivered to fuel injector 66 by a fuel system(not shown) including a fuel tank, a fuel pump, and a fuel rail.

Ignition system 88 can provide an ignition spark to combustion chamber30 via spark plug 92 in response to spark advance signal SA fromcontroller 12, under select operating modes. Though spark ignitioncomponents are shown, in some embodiments, combustion chamber 30 or oneor more other combustion chambers of engine 10 may be operated in acompression ignition mode, with or without an ignition spark. In someembodiments, the ignition system may include a dual spark system whichincludes two spark plugs per cylinder (not shown).

Intake passage 42 may include throttles 62 and 63 having throttle plates64 and 65, respectively. In this particular example, the positions ofthrottle plates 64 and 65 may be varied by controller 12 via signalsprovided to an electric motor or actuator included with throttles 62 and63, a configuration that is commonly referred to as electronic throttlecontrol (ETC). In this manner, throttles 62 and 63 may be operated tovary the intake air provided to combustion chamber 30 among other enginecylinders. The positions of throttle plates 64 and 65 may be provided tocontroller 12 by throttle position signals TP. Intake passage 42 mayinclude a mass air flow sensor 120 and a manifold air pressure sensor122 for providing respective signals MAF and MAP to controller 12.Further, intake passage 44 may include charge motion control valve 45for controlling the intensity of charge motion occurring in combustionchamber 30.

Further, in the disclosed embodiments, an exhaust gas recirculation(EGR) system may route a desired portion of exhaust gas from exhaustpassage 48 to intake passage 44 via high-pressure EGR (HP-EGR) passage140. Although the system is described using HP-EGR, in some examples, alow-pressure EGR (LP-EGR) passage may also or alternatively be included.In implementations where the engine is not turbocharged, anaturally-aspirated EGR may also be employed. The amount of EGR providedto intake passage 44 may be varied by controller 12 via HP-EGR valve142. In some embodiments, a throttle may be included in the exhaust toassist in driving the EGR. Further, an EGR sensor 144 may be arrangedwithin the EGR passage and may provide an indication of one or more ofpressure, temperature, and concentration of the exhaust gas.Alternatively, the EGR may be controlled through a calculated valuebased on signals from the MAF sensor (upstream), MAP (intake manifold),MAT (manifold gas temperature) and the crank speed sensor. Further, theEGR may be controlled based on an exhaust O₂ sensor and/or an intakeoxygen sensor (intake manifold). Under some conditions, the EGR systemmay be used to regulate the temperature of the air and fuel mixturewithin the combustion chamber. FIG. 1 shows a high-pressure EGR systemwhere EGR is routed from upstream of a turbine of a turbocharger todownstream of a compressor of a turbocharger. Further, as shown in FIG.1, the HP-EGR system may include HP-EGR cooler 146 to transfer heat fromthe EGR gasses to engine coolant, for example.

According to the present description, HP-EGR 140 is combined withexhaust gas recovery line 141 (EGHR). Thus, for simplicity, an exhaustsystem configured according to the present disclosure may include abranched path that allows heat from exhaust gasses to be transferred tothe coolant without recirculation of the exhaust gasses back to anengine intake. As one example, an EGHR line may be added to the exhaustsystem with a parallel arrangement to the main exhaust flow, whichallows for a compact packing in the engine compartment. Moreover,another branch running from the exhaust pipe to the intake manifold mayinclude an air-to-liquid heat exchanger in order to transfer heat fromthe exhaust flow to the engine coolant. Valves then allow the system toperform multiple functions in the manner described below. The amount ofEGHR provided may be varied by controller 12 via EGHR valve 143.

Engine 10 may further include a compression device such as aturbocharger or supercharger including at least a compressor 162arranged along intake passage 44 in some embodiments. For aturbocharger, compressor 162 may be at least partially driven by aturbine 164 (e.g., via a shaft) arranged along exhaust passage 48. For asupercharger, compressor 162 may be at least partially driven by theengine and/or an electric machine, and may not include a turbine. Thus,the amount of compression provided to one or more cylinders of theengine via a turbocharger or supercharger may be varied by controller12.

Exhaust gas sensor 126 is shown coupled to exhaust passage 48 upstreamof emission control system 71 and downstream of turbine 164. Sensor 126may be any suitable sensor for providing an indication of exhaust gasair/fuel ratio such as a linear oxygen sensor or UEGO (universal orwide-range exhaust gas oxygen), a two-state oxygen sensor or EGO, a HEGO(heated EGO), a NO_(x), HC, or CO sensor.

Emission control device 71 is shown arranged along exhaust passage 48downstream of exhaust gas sensor 126. Emission control devices 71 may bea selective catalytic reduction (SCR) system, three way catalyst (TWC),NO_(x) trap, various other emission control devices, or combinationsthereof. For example, device 71 may be a TWC and device 72 may be aparticulate filter (PF). Further, in some embodiments, during operationof engine 10, emission control device 71 may be periodically reset byoperating at least one cylinder of the engine within a particularair/fuel ratio. In some embodiments, one or the other of devices 71 and72 may be present in engine 10.

Controller 12 is shown in FIG. 1 as a microcomputer, includingmicroprocessor unit 102, input/output ports 104, an electronic storagemedium for executable programs and calibration values shown as read onlymemory chip 106 in this particular example, random access memory 108,keep alive memory 110, and a data bus. Controller 12 may receive varioussignals from sensors coupled to engine 10, in addition to those signalspreviously discussed, including measurement of inducted mass air flow(MAF) from mass air flow sensor 120; engine coolant temperature (ECT)from temperature sensor 112 coupled to cooling sleeve 114; a profileignition pickup signal (PIP) from Hall effect sensor 118 (or other type)coupled to crankshaft 40; throttle position (TP) from a throttleposition sensor; and absolute manifold pressure signal, MAP, from sensor122. Engine speed signal, RPM, may be generated by controller 12 fromsignal PIP. Manifold pressure signal MAP from a manifold pressure sensormay be used to provide an indication of vacuum, or pressure, in theintake manifold. Note that various combinations of the above sensors maybe used, such as a MAF sensor without a MAP sensor, or vice versa.During stoichiometric operation, the MAP sensor can give an indicationof engine torque. Further, this sensor, along with the detected enginespeed, can provide an estimate of charge (including air) inducted intothe cylinder. In one example, sensor 118, which is also used as anengine speed sensor, may produce a predetermined number of equallyspaced pulses every revolution of the crankshaft.

Storage medium read-only memory 106 can be programmed with computerreadable data representing instructions executable by processor 102 forperforming the methods described below as well as other anticipatedvariants not specifically listed.

As described above, FIG. 2 shows only one cylinder of a multi-cylinderengine, and each cylinder may similarly include its own set ofintake/exhaust valves, fuel injector, spark plug, etc.

Turning to a description of the exhaust system configured with combinedEGR and EGHR devices, FIGS. 3-6 show example systems according to thepresent disclosure.

As one example, the exhaust system of a vehicle may comprise an EGRcooler, an exhaust gas heat recovery line coupled to the EGR cooler, anEGR valve downstream of the EGR cooler for controlling exhaust flow toan engine intake, and a valve located within the exhaust heat recoveryline for controlling a rate of exhaust flow therethrough, the rate ofexhaust flow determining an amount of heat transferred to an enginecoolant. In some example embodiments, the system includes the exhaustgas heat recovery line coupled to the EGR cooler via a branch downstreamof the EGR cooler, the exhaust gas heat recovery line further connectingto an exhaust passage, wherein the connection to the exhaust passage isupstream of an exhaust catalyst. However, the connection to the exhaustpassage may also be positioned downstream of an exhaust catalyst asdescribed in greater detail below. To increase an exhaust flow throughthe EGR and/or EGHR device, the exhaust system may further comprise anexhaust throttle positioned in the exhaust passage upstream of theconnection between the exhaust gas heat recovery line and exhaustpassage upstream of the catalyst. In other embodiments, the valvelocated in the exhaust heat recovery line may be a passive one-way valvethat is opened responsive to an exhaust flow above a threshold. In stillother embodiments, an inlet valve may be positioned in the EGR coolerupstream of the EGR cooler. In still further embodiments, the exhaustgas heat recovery line may be coupled to the EGR cooler in an alternatearrangement. For example, the exhaust gas heat recovery line may becoupled to the EGR cooler on an upstream side rather than on thedownstream side. Thus, the valves located within the exhaust gas heatrecovery line may be positioned upstream of the EGR cooler. To reducethe size within the engine compartment, and to further enhance systempackaging, the exhaust system may be configured with the exhaust gasheat recovery line positioned near an exhaust manifold parallel to theexhaust passage.

FIG. 3 illustrates first exemplary configuration 300 wherein example EGRcooler 140 is coupled to EGHR line 141, and wherein the EGHR outletconnects to the exhaust passage upstream of a catalyst, e.g., device 71.For simplicity, engine 10 is shown schematically as a four cylinderengine having an inline arrangement. However, other engine arrangementsmay alternatively be used. For example, the above technology can beapplied to V-6, I-4, I-6, V-12, opposed 4, and other engine types.Intake air from intake passages 44 (e.g., one intake passage is labeled)is directed to intake manifold 304 and further into cylinders 30 wherecombustion occurs. After combustion, exhaust gasses are directed toexhaust passages 48 (e.g., one exhaust passage is labeled) whereindividual exhaust flows from each cylinder are shown being combinedinto exhaust pipe 348, for example. Thereafter, exhaust gasses may bedirected along the various pathways according to the methods described.In FIG. 3, exhaust passage 348 includes exhaust throttle 366, inaddition to EGR valve 142 and EGHR valve 143 that are used to adjust oneor more exhaust flow paths during operation.

Valve actuation allows for exhaust gasses to be redirected through thevarious passages shown. In some instances, all, none, or a portion ofthe exhaust gasses may be redirected based on the engine conditionsidentified. In other words, the exhaust flow may be distributed througheach of the pathways independently, or as a combination of two or moreof the pathways thereof. For example, under a first set of someconditions, the vehicle may be operated in a first operating mode torelease exhaust gases directly via exhaust manifold 348. In this way,the hybrid vehicle is described based on different operating modes thatredirect exhaust flows throughout the exhaust system before exiting thevehicle via an exhaust pipe. As another example, under a second set ofconditions, the vehicle may be operated in a second operating mode totransfer heat to the engine coolant by directing exhaust gases to EGHR141. Likewise, under a third set of conditions different from theothers, the vehicle may be operated in a third operating mode torecirculate exhaust gasses to engine 10 by directing the exhaust flow tointake manifold 304. For simplicity, during these operating modes (e.g.,first through third modes), the description presented adjustssubstantially all of the exhaust flow along the indicated pathways.However, under yet a different set of conditions referred to as a fourthset of conditions, the vehicle may be operated in a fourth operatingmode to distribute the exhaust gasses through two or more of thepathways (e.g., 50% of the flow to direct exhaust and 50% of the flow toEGHR) based on the engine operating conditions. The methods aredescribed with respect to adjustments made to heat a vehicle cabin afteran engine cold start. However, this is non-limiting and other examplesituations and operating scenarios are possible. For instance, theengine coolant may also be heated to increase the operating efficiencyof the engine by lowering the oil viscosity.

As noted above already, when starting a hybrid vehicle in coldconditions, it is desirable to warm up the engine coolant as quickly aspossible to allow the engine of the hybrid vehicle to be turned off toreduce fuel consumption during operation. Heating of the engine coolantallows for warming of the cabin since heated engine coolant is routed tothe heater core to heat the cabin air. Heat generated by the enginerepresents a major source of heat for warming the vehicle passengercompartment. For this reason, the engine may continue to operate until asatisfactorily high coolant temperature is attained based on a desiredcabin temperature indicated by the vehicle operator.

When EGR valve 142 is at least partially open, a cooled EGR function isenabled. EGHR valve 143 thus acts to prevent uncooled exhaust gas fromthe exhaust passage from entering the intake manifold. When EGR valve142 is open and exhaust throttle 366 is closed partially, the EGRfunction is enhanced by raising the pressure at the EGR branch inlet,which increases a flow of exhaust gas recirculation into the intakemanifold. When EGR valve 142 is closed and EGHR valve 143 is at leastpartially opened, an EGHR function is enabled. Closing exhaust throttle366 may be used to control the pressure difference between the inlet andoutlet branches of the combined EGR/EGHR system. A pressure differentialacross exhaust throttle 366 causes exhaust gas to flow through EGRpassage 140 and EGHR line 141 where heat is transferred to the enginecoolant via the heat exchanger. When EGHR valve 143 is an active valve,the rate of flow through EGHR line 141 may be adjusted via the EGHRvalve. However, when EGHR valve 143 is a passive valve, the rate ofexhaust flow may be adjusted based on one or more of exhaust throttle366 and EGR valve 142. When EGR valve 142 is at least partially open andEGHR valve 143 is at least partially open, both exhaust gas heatrecovery and cooled EGR functions are enabled. The degree of opening ofeach valve may be used to control the flow and thereby distribution ofgasses into each of intake manifold 304 and the exhaust gas heatrecovery line EGHR 141. When exhaust flows are simultaneouslydistributed through both lines, exhaust throttle 366 may be actuated tocontrol the rate of flow through both lines. As noted above, increasingthe degree of closing of exhaust throttle 366 may increase the pressuredifferential between the inlet and outlet branches of the EGR/EGHRsystem, which increases the rate of flow of the gasses through thecombined EGR/EGHR lines.

Various example embodiments of the present disclosure may be configuredto provide similar functions but with different or reduced plumbingand/or valve arrangements. For example, in one arrangement EGHR valve143 may be a passive one-way valve (e.g., a check valve). With thisconfiguration, pressure from exhaust throttle 366 forces the check valveopen at a predetermined threshold. Thus, when exhaust gas heat recoveryis utilized, exhaust throttle 366 may be actuated to a partially orfully closed position, which creates a force that causes the passiveone-way valve, e.g., EGHR valve 143, open. Conversely, when cooled EGRis to be utilized, either alone or in combination with exhaust gas heatrecovery, the check valve may prevent uncooled exhaust gas from beingrecirculated back into the intake manifold via EGHR line 141.

FIG. 4 illustrates a second exemplary configuration 400 with a reducedvalve configuration. In FIG. 4, EGHR valve 443 is a combination of anexhaust throttle valve and an outlet valve. For example, EGHR valve 443may take the form of either a flapper door or a butterfly valve in someimplementations. Thus, when EGHR valve 443 is closed, uncooled exhaustgas is prevented from being recirculated into the intake manifold viaEGHR line 141. However, when EGHR valve 443 is opened, the exhaust flowmay be simultaneously throttled in exhaust manifold 348 (e.g., the mainexhaust pipe) and also allowed to flow through the EGHR device to theoutlet of the exhaust branch. In this way, opening EGHR valve 443provides a pressure drop that induces exhaust flow through the heatexchanger while also permitting exhaust gas to be released directly viathe exhaust pipe. In some embodiments, an upstream inlet valve may beincluded in EGR passage 140 upstream of HP-EGR cooler 146 to furthercontrol exhaust flow through the EGR cooler.

FIG. 5 illustrates a third exemplary configuration 500 with an EGHRoutlet line connecting to the exhaust passage downstream of the firstcatalyst (e.g., device 71). As shown, the outlet of the branch isrelocated to a position downstream of the catalyst. When EGHR valve 143is opened, a pressure drop across the catalyst develops that inducesexhaust flow through EGHR line 141. When configured with thisarrangement, actuation of the volume of exhaust flow through the branchof EGHR line 141 may also account for the catalytic activity of thecatalyst to allow the vehicle to sufficiently catalyze the exhaustgasses before release to the atmosphere, in addition to heating theengine coolant via the exhaust heat transferred to the engine coolantvia a heat exchanger.

FIG. 6 illustrates a fourth exemplary configuration 600 where the inletof the EGR cooler couples to the EGHR at a downstream position of theEGHR line. With this arrangement, EGHR valve 143 positioned downstreamof EGHR line 141 may simultaneously throttle the exhaust flow while alsoactuating the rate of flow through the exhaust gas recovery line. WhenEGHR valve 143 is open and EGR valve 142 is closed, heat from theexhaust may be transferred to the engine coolant. Alternatively, whenEGR valve 142 is open, exhaust flow through EGR line 140 may occur inthe direction indicated by the arrows. In the same manner describedabove, exhaust may be made to flow throughout the various pathwaysindicated by the flow arrows by adjusting valves within the exhaustsystem. Therefore, although the arrangement is different, the combinedEGR and EGHR exhaust system may also allow for the heat from the exhaustgasses to be transferred to the coolant under various conditions, e.g.,cold conditions. As shown, the heat exchanger, e.g., HP-EGR cooler 146may alternatively be configured in some instances to simultaneouslyextract heat from both EGR passage 140 and EGHR line 141.

Turning now to a description of the methods, FIGS. 7 and 8 show exampleflow charts for switching operational exhaust modes by adjusting theexhaust flow pathway according to the present disclosure.

FIG. 7 shows example flow chart 700 for switching operating modes of theexhaust system by adjusting an exhaust flow pathway via one or morevalve adjustments. As noted above, the operating modes are describedwith respect to exhaust flows through each pathway (e.g., through theexhaust passage, EGR line or EGHR line), and via a combination of thevarious pathways (e.g., via two or more of the lines) for simplicity.Operational adjustments indicated in FIG. 7 are described with respectto the first example configuration 300 of FIG. 3.

At 702, method 700 includes determining the engine operating conditions.For example, an engine temperature and/or coolant temperature may bedetermined to identify whether heat is to be transferred to the coolantduring engine operation. The example provided herein is an engine coldstart wherein exhaust heat is transferred to the coolant from the engineexhaust. The advantage of the disclosed exhaust system and operatingmethods is that the rate of coolant heating (e.g., and thereby the rateof the vehicle cabin heating) can be controlled based on the amount ofheat transferred to the coolant during operation since a substantialamount of heat may be released from the engine of the vehicle throughthe exhaust pipe. Redirecting the exhaust flow to the exhaust gasrecirculation line coupled to the exhaust gas heat recovery lineadvantageously allows for at least a portion of heat from the engine tobe transferred to the engine coolant during operation. In particular,the methods described allow for the heat to be recovered from theexhaust regardless of the on/off state of the EGR. In other words, theexhaust gas heat recovery is not limited to the EGR flow since up to100% of the exhaust flow can be routed to the heat exchanger or exhaustgas heat recovery line for heat recovery (e.g., by closing EGR valve 142and exhaust throttle 366, and opening EGHR valve 143).

Based on the engine operating conditions, at 704, method 700 maydetermine whether the vehicle is to be operated in the 1^(st) exhaustmode. If the 1^(st) exhaust mode is indicated based on, e.g., a firstset of conditions, then one or more valve adjustments may be made torelease exhaust gasses directly via the exhaust manifold or passage, asindicated at box 706. For example, EGR valve 142 and EGHR valve 143 maybe closed (e.g., actuated to a closed position), which causes exhaustedgasses to be released directly via the exhaust pipe (or exhaustpassage).

Alternatively, if the controller (e.g., controller 12), determines thatthe conditions are such that the vehicle is to be operated in anotheroperating mode, method 700 proceeds to box 710 where a decision is madewith regard to vehicle operation via the 2^(nd) exhaust mode to directexhaust gas through the exhaust gas heat recovery line whiletransferring heat to the coolant. If the vehicle is to be operated inthe 2^(nd) exhaust mode, for example, because a second set of conditionsare identified that are different from the first set of conditions, oneor more valve adjustments may be made to direct exhaust gasses throughEGHR line 141 to transfer heat to the coolant, as indicated at box 712.As one example, EGR valve 142 and exhaust throttle 366 may be closedwhile EGHR valve 143 is opened to adjust the exhaust airflow pathwaythrough EGHR line 141.

If the exhaust is not to be operated in the 2^(nd) exhaust mode at box710, method 700 proceeds to box 720 where a decision is made withregards to exhaust gas recirculation. If the vehicle is to be operatedin the 3^(rd) exhaust mode, for example, because a third set ofconditions are identified that are different from either the first orsecond sets of conditions, one or more valve adjustments may be made todirect at least a portion of the exhaust gasses through the EGR line andback into the engine intake, for example, to reduce emissions byrecirculating the exhaust flow back into the engine, as indicated at box722. As one example, EGR valve 142 may be open and exhaust throttle 366actuated based on engine operating conditions while EGHR valve 143 isclosed. These valve adjustments allow the exhaust flow path to bedirected through EGR line 140 and toward the engine intake, e.g., intakemanifold 304. In some instances, a higher or increased EGR flow may beachieved by throttling the exhaust valve. For example, the exhaust valvemay be throttled while the intake vacuum is reduced to increase a rateof exhaust flow through the EGR cooler.

The fourth exhaust mode indicated by box 720 refers to a distributedflow of exhaust through both the EGR and EGHR lines, in addition to theexhaust passage. In other words, the exhausted gasses are directedthrough the exhaust pathways indicated based on engine operatingconditions and a desired coolant heating rate. In this way, one or moreof the valves may be adjusted or actuated to a position that distributesthe exhaust flow throughout the various lines based on the conditionsidentified.

Although the exhaust flows have been described simply based on valveon/off states in the 1^(st), 2^(nd), and 3^(rd) operating modes, in anexhaust system on-board a vehicle, exhaust gasses may be distributedthroughout a combination of pathways under substantially all conditions.Therefore, the various exhaust modes indicated may also be implementedand managed based on coolant heating and exhaust flow conditionsanticipated during the engine drive cycle. For example, under hotconditions (e.g., engine temperature exceeding a temperature threshold)engine heat may be released from the vehicle through the exhaust piperather than transferring the heat to the engine coolant via a heatexchanger, e.g., a radiator. Alternatively, under cold conditions,engine heat may be transferred to the coolant for use on-board thevehicle while a portion of the exhaust gas is released via the exhaustpassage.

The methods may be implemented within a device comprising an EGR coolercoupled to an exhaust gas heat recovery line. As described, the methodsmay comprise actuating an EGR valve downstream of the EGR cooler toadjust a flow of exhaust gas to an engine intake and a flow of exhaustgas to the exhaust gas heat recovery line, and controlling an amount ofheat transferred from the flow of exhaust gas distributed to the exhaustgas heat recovery line to an engine coolant via a heat exchanger.According to the description, control of the heat transfer may compriseopening the EGR valve to increase the flow of exhaust gas to the engineintake while simultaneously decreasing the flow of exhaust gas to theexhaust gas heat recovery line, wherein closing the EGR valve increasesthe flow of exhaust gas to the exhaust gas heat recovery line whilesimultaneously decreasing the flow of exhaust gas to the engine intake.However, inclusion of an exhaust throttle may further control a flow ofexhaust gas to the EGR cooler by actuation of the exhaust throttle.

As one example, FIG. 8 illustrates method 800 for switching operatingmodes of the exhaust system by adjusting the exhaust flow pathway basedon the engine operating conditions. At 810, the controller (e.g.,controller 12) determines the on/off state of the engine. If the engineis on and running, method 800 proceeds to decision block 820 wherecontroller 12 further determines whether the coolant is to be heated,for instance, because the coolant temperature falls below a temperaturethreshold. Alternatively, if the engine is off while the vehicle isoperated, controller 12 may be configured to provide power to thevehicle via an alternate power source such as an electric motor.

At 820, the controller further determines whether the coolant is to beheated and whether at least a portion of the exhaust gas is to be routedback to the engine as indicated at boxes 830 and 840, which produces thefour operating modes identified above.

For example, if coolant heating is to occur (e.g., yes at decision box820) and controller 12 determines that no exhaust gas is to be directedto the engine (e.g., no at decision box 830), valve adjustments may bemade to operate the exhaust in the second exhaust mode by directingexhaust gas through the exhaust gas heat recovery line to transfer heatto the coolant as indicated at box 834. In some instances, the secondexhaust mode may include releasing the exhaust gas via both the exhaustgas heat recovery line as well as directly via the exhaust passage whiletransferring heat to the coolant. However, in other instances, up to100% of the exhaust gas may be directed through the exhaust gas heatrecovery line to increase the heat transferred to the coolant duringoperation. Moreover, if coolant heating is to occur (e.g., yes atdecision box 820) and controller 12 determines that at least a portionof the exhaust gas is to be recirculated to the engine based on theengine operating conditions (e.g., yes at decision box 830), valveadjustments may be made in the manner already described to adjust thevehicle operation to the fourth exhaust mode wherein a portion of theexhaust gasses are directed back into the engine intake while theexhaust gasses are also routed through the exhaust heat recovery lineand the exhaust passage as indicated at box 832. In this way, thedistribution of the exhausted gasses can be adjusted by adjusting a flowof air throughout the various exhaust lines during vehicle operation tocontrol the amount of heat transferred to the coolant, and thereby arate of coolant heating.

Alternatively, if no coolant heating is to occur (e.g., no at decisionbox 820) and controller 12 determines that no exhaust gas is to bedirected to the engine (e.g., no at decision box 840), valve adjustmentsmay be made to operate the exhaust in the first exhaust mode byreleasing the exhaust gasses directly via the exhaust passage asindicated at box 844. However, if no coolant heating is to occur (e.g.,no at decision box 820) and controller 12 determines that at least aportion of the exhaust gas is to be directed to the engine based on theengine operating conditions (e.g., yes at decision box 840), valveadjustments may be made to operate the exhaust in the third exhaust modeby recirculating the exhaust gasses back into the engine intake asindicated at box 842. For example, at least a portion of the exhaustgasses may be recirculated to the engine while the remaining exhaustgasses are released directly via the exhaust passage.

FIG. 9 shows example flow chart 900 for rapidly heating the cabin airtemperature by controlling exhaust flow to the EGHR line according tothe present disclosure. As described herein, the methods mayadvantageously provide for the efficient and rapid recovery of heat fromthe engine during operation. For simplicity, the methods are describedwith respect to warming a vehicle cabin after an engine cold start.However, other examples are possible and fall within the scope of thepresent disclosure.

In this way, method 900 may be a method for heating engine coolantduring engine warm-up, comprising transferring heat from an exhaust flowto the engine coolant via a heat exchanger positioned in an exhaust gasheat recovery line responsive to an EGR valve position. As one example,the EGR valve position may be continuously variable and therefore usedto determine a rate of exhaust flow to the exhaust gas heat recoveryline, the exhaust flow rate being used to control the amount of heattransferred to the engine coolant based on engine conditions. Thus, whenthe EGR valve is opened, a rate of EGR flow to the engine may also beincreased, the increased flow rate to the engine decreasing the rate offlow to the exhaust gas heat recovery line. However, when an EGHR valveis included and coupled to the exhaust gas heat recovery line to controlthe flow rate therethrough, the EGR valve and EGHR valves may beadjusted independently or synchronously to control the rate of exhaustflow to the exhaust gas recovery line to control the heat transferred tothe coolant. The heat transferred to the coolant is increased toincrease the rate of heating in a vehicle cabin. In addition, when aseparate EGHR valve is included, the rate of flow to the exhaust gasheat recovery line may occur independently of EGR operation when the EGRvalve is closed. An exhaust throttle placed in an exhaust passage mayfurther increase a rate of flow to one or more of the engine and theexhaust gas heat recovery line, as described in greater detail above.Because the method is described with respect to a cold start on-board ahybrid vehicle, the methods may further comprise shutting the engine offresponsive to a cabin air temperature in excess of a temperaturethreshold, the cabin air temperature being increased responsive to theheat transferred to the engine coolant.

At 902, method 900 includes determining whether the vehicle hasundergone an engine cold start. For instance, an engine not used for ashort period of time may cool to the point where a temperature (e.g., anengine temperature) falls below a threshold. If a cold start isidentified, method 900 proceeds to box 910 where a determination is madewhether the vehicle cabin is to be heated. However, if the engineconditions are such that an engine cold start is not to be performed,method 900 proceeds to box 904 by making valve adjustments to releaseheat directly via the exhaust manifold or passage. For example, asdescribed with respect to method 700 of FIG. 7, both EGR and EGHR valvesmay be closed to operate the exhaust system in the 1^(st) exhaust modewhile exhausting engine gasses directly via the exhaust passage.

Returning to box 910, if the vehicle cabin is to be heated, method 900proceeds to box 912 by transferring heat to the coolant to further heatthe vehicle cabin. For example, the EGHR valve may be opened to producean increased rate of flow to the EGHR. As one example, substantially all(e.g., 100% in the 2^(nd) exhaust mode) of the exhaust flow may berouted through the EGHR line to transfer heat to the engine coolant.However, as another example, a portion of the exhaust flow may be routedthrough the EGHR line while the rest of the flow is routed through theexhaust pipe and/or the EGR line to the engine. Furthermore, in someinstances, the amount of exhaust flow routed through the EGHR line maybe based on the amount of heat transferred and thereby the rate ofheating desired in the vehicle cabin. In this way, the amount of heattransferred to the coolant may be adjusted to achieve an optimal cabinheating rate, which allows for the ambient air to be warmed quickly.Alternatively, if no cabin heating is desired, for example, becausecontroller 12 determines that the ambient temperature exceeds atemperature set point indicated by a heating unit or a vehicle operatorhas manually adjusted a heater control command, method 900 proceeds tobox 904 and actuates an amount of exhaust gas recirculation based on theengine operating conditions.

Returning to box 912, upon engaging the exhaust gas heat recovery unit,method 900 proceeds to box 920 where a determination is made with regardto the extent of heating. In this way, a temperature threshold may beincluded that indicates the temperature of the vehicle cabin. Then, ifthe cabin temperature exceeds the temperature threshold, method 900 maymake operational adjustments based on the temperature above thetemperature threshold to shut off the engine while providing power tothe vehicle via an alternate power source. For example, a hybrid vehiclemay also include an electric motor powered by an electric power supplyin addition to the engine. Thus, power supplied by the vehicle may beprovided by the motor, which results in reduced fuel use and therebyreduced emissions. If the cabin temperature falls below the temperaturethreshold, the system may continue to actuate the rate of flow throughthe EGHR line as the rate of heat transfer to the coolant is managedwhile heating the vehicle cabin. Then, once the cabin has warmed up, at922 the engine may be shut off and the vehicle powered via the alternatepower source residing on-board the vehicle. Method 900 thus furthercomprises shutting the engine off responsive to one or more of a cabinair temperature in excess of a temperature threshold, the cabin airtemperature being adjusted responsive to heat transferred to the enginecoolant, and a heater control command. For example, a vehicle operatormay manually adjust a heater control command by pushing a knob or buttonto reduce the amount of heat that warms up the vehicle cabin.

FIG. 10 shows an example cold start operating sequence of a hybridvehicle to illustrate the methods just described. In FIG. 10, anexemplary engine load 1010 is shown in the top plot along with thevarious exhaust flow paths indicated (e.g., 1020, 1030, and 1040) forthe exemplary reduced valve configuration of FIG. 4. The EGR and EGHRvalve positions (e.g., 1050 and 1060, respectively) are also shown. Timeis shown along the x-axis and time increases from left to right.

At T₀, the vehicle is engaged under cold start conditions. Thereafter,engine load 1010 increases as the vehicle is driven. During the timeperiod from T₀ to T₁, the exhaust flow is directed through the EGHR lineto transfer the engine heat to the engine coolant. As such, the directexhaust 1020, that is, the exhaust flow released directly through theexhaust pipe, is maintained at a minimal level. In some instances, theminimal level is substantially zero. As shown, EGHR flow 1030 increasesin proportion to the engine load as the heat from the exhaust flow isrecovered via the heat exchanger, e.g., EGR cooler 146, duringoperation. EGR flow 1040 may be controlled based on engine operatingconditions; however the engine operating conditions may dictate that noEGR flow occurs during an engine cold start. For this reason, the EGRflow is shown constant (e.g., at minimum level) for simplicity. Areduced rate of flow through the EGR line allows for an increased rateof flow through the EGHR line. During operation, EGR and EGHR valveadjustment may occur such that an enhanced heat recovery occurs eventhough the engine operates under the colder engine operating conditions.In view of the exhaust flows just described, EGR valve 1050 may beadjusted to the closed position whereas EGHR valve 1060 is adjusted tothe open position to produce the cooled exhaust flow indicated.According to the reduced valve configuration of FIG. 4, EGHR valve 443is a combination of an exhaust throttle valve and an outlet valve. Thus,when EGHR valve 443 is open, the exhaust flow is simultaneouslythrottled in exhaust manifold 348 (e.g., to reduce a flow in the mainexhaust pipe) and allowed to flow through the EGHR device to the outletof the exhaust branch.

From T₁ to T₂, the load on the engine increases to a point whereemissions released from the engine exceed a threshold (not shown). Inresponse to this condition, a portion of the exhaust flow is directedthrough the EGR line to recirculate the exhaust gasses as well as to theEGHR line to transfer engine heat to engine coolant. No adjustments aremade to direct exhaust 1020, which is maintained at the minimal level.EGHR flow 1030 is reduced as some of the exhaust flow is redirected tothe EGR during operation. EGR flow 1040 is thus proportionally increasedwhile EGHR flow 1030 is reduced. In some instances, the total flow maystill be reflective of engine load 1010. In this way, the exhaust systemaccording to the present disclosure allows for simultaneous optimizationof heat transfer to the coolant and reduction of emissions via EGR.Based on the exhaust flows shown, EGR valve 1050 may be adjusted to anopen position and further actuated during operation based on a set ofdesired emissions, which may be measured by a sensor in the exhaustsystem. EGHR valve 1060 may also be adjusted based on the engine loadand actuated responsive to the EGR flow and identified conditions.

From T₂ to T₃, the engine is operated at a high load and so produceshigher levels of emissions. Thus, emissions released from the engine maycontinue to exceed the threshold (not shown). Engine emissions maydepend on engine temperature. Thus, as the vehicle is driven longer, thetemperature of the engine may also increase, which changes theefficiency of exhaust emissions during operation. In some embodiments,vehicle emissions may be estimated and/or calculated, e.g., via a model,to determine the vehicle emissions expected for a given set of operatingconditions. Although the temperature of the cabin may increase duringthe operating sequence, controller 12 may monitor the cabin temperaturewhile the temperature falls below the temperature threshold, asdescribed with respect to FIG. 9. In response to the increased engineload, the exhaust flow may be at least partially directed through theEGR line to recirculate exhaust gasses while preventing exhaust flowthrough the EGHR line. No adjustments are made to direct exhaust 1020,which is maintained at the minimal level. EGHR flow 1030 is reduced to aminimal level as a portion of the exhaust flow is redirected to the EGRduring operation to reduce emissions by increasing the rate of exhaustgas recirculation. EGR flow 1040 is thus increased to a maximal levelbased on the engine operating conditions while EGHR flow 1030 is reducedto a minimal level. As one example, the rate of flow through the EGRline may be increased to a maximal level that is a flow rate of about25% of the inlet flow rate. In this way, the exhaust system allows forcooled EGR via the exhaust valve adjustment. Based on the exhaust flowsshown, EGR valve 1050 may be actuated to the open position whereas EGHRvalve 1060 may be adjusted to the closed position.

From T₃ to T₄, the load on the engine decreases and thus the amount ofexhaust emissions generated are reduced. In response, adjustments may bemade to direct a portion of the exhaust flow through the EGHR line againto transfer engine heat to engine coolant while the exhaust flow throughthe EGR is turned off (e.g., because the emissions are reduced and fallbelow a threshold). No adjustments are made to direct exhaust 1020,which is maintained at the minimal level. EGHR flow 1030 is increasedbased on the engine load while EGR flow 1040 is reduced. In this way,the exhaust system continues transferring heat to the coolant to warm upthe vehicle cabin. Based on the exhaust flows shown, EGR valve 1050 maybe actuated to the closed position while EGHR valve 1060 is actuated tothe open position and adjusted based on engine load.

From T₄ to T₅, the load on the engine fluctuates based on the drivingconditions. During this period, a portion of the exhaust flow may bereleased via the exhaust pipe. Thus, valve adjustments are made to theEGHR valve to adjust the exhaust flow while adjusting the rate of heattransferred to the coolant. In response, a portion of the exhaust flowthrough the EGHR line may be reduced while the exhaust flow through theexhaust pipe is increased. No adjustments are made to EGR flow 1040,which is maintained at the minimal level. The exhaust system continuestransferring heat to the coolant to warm up the vehicle cabin but at alower rate. However, because the rate of heat transfer may depend on theengine temperature in some instances, the exhaust flow through theexhaust passage may be increased while exhaust flow through the exhaustgas heat recovery line is decreased to heat the vehicle cabin. Forexample, operational adjustments may be made to increase the amount ofexhaust flow directed to the catalyst based on engine operatingconditions. EGR valve 1050 may thus be maintained in the closed positionwhile EGHR valve 1060 is in the open position.

At T₅, the cabin temperature exceeds the temperature threshold, theengine shut off and power provided by an alternate power source such asan electric motor (not shown). In this way, the load on the engine maybe shutoff or reduced to a minimal level. Thereafter, the exhaust flowsmay also be prevented since combustion no longer occurs in the engine.EGR valve 1050 is maintained in the closed position while EGHR valve1060 is adjusted to the closed position. However, in some instances, thevalves may simply be held at their respective positions when engine shutoff occurs since engine exhaust is no longer produced. Then, when theengine is reengaged, one or more adjustments may be made to distributethe exhaust flow throughout the exhaust system in the manner alreadydescribed.

In this way, a reduced mass, highly efficient exhaust gas heat exchangeris presented. In addition, the multi-functional exhaust unit may beoperated in different modes to route exhaust gases through differentpaths during operation. In one particular example, the combined EGR andEGHR exhaust system is used to warm up the engine coolant quickly undercold conditions. For example, it may be desirable to route exhaust gasto the heat exchanger while also avoiding an excess thermal load on theradiator. Furthermore, the system according to the present disclosureallows for a reduced size, weight and cost when implemented into avehicle as described.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory. The specific routinesdescribed herein may represent one or more of any number of processingstrategies such as event-driven, interrupt-driven, multi-tasking,multi-threading, and the like. As such, various actions, operations,and/or functions illustrated may be performed in the sequenceillustrated, in parallel, or in some cases omitted. Likewise, the orderof processing is not necessarily required to achieve the features andadvantages of the example embodiments described herein, but is providedfor ease of illustration and description. One or more of the illustratedactions, operations and/or functions may be repeatedly performeddepending on the particular strategy being used. Further, the describedactions, operations and/or functions may graphically represent code tobe programmed into non-transitory memory of the computer readablestorage medium in the engine control system.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. An exhaust system of a vehicle, comprising: an EGR cooler, an exhaustgas heat recovery line coupled to the EGR cooler, an EGR valvedownstream of the EGR cooler for controlling exhaust flow to an engineintake, and a valve located within the exhaust gas heat recovery linefor controlling a rate of exhaust flow therethrough, the rate of exhaustflow determining an amount of heat transferred to an engine coolant. 2.The exhaust system of claim 1, wherein the exhaust gas heat recoveryline is coupled to the EGR cooler via a branch downstream of the EGRcooler, the exhaust gas heat recovery line further connecting to anexhaust passage.
 3. The exhaust system of claim 2, wherein theconnection to the exhaust passage is upstream of an exhaust catalyst. 4.The exhaust system of claim 2, wherein the connection to the exhaustpassage is downstream of an exhaust catalyst.
 5. The exhaust system ofclaim 3, further comprising an exhaust throttle positioned in theexhaust passage upstream of the connection between the exhaust gas heatrecovery line and exhaust passage upstream of the catalyst.
 6. Theexhaust system of claim 5, wherein the valve located in the exhaust gasheat recovery line is a passive one-way valve.
 7. The exhaust system ofclaim 5, further including an inlet valve positioned in the EGR coolerupstream of the EGR cooler.
 8. The exhaust system of claim 1, whereinthe exhaust gas heat recovery line is coupled to the EGR cooler on anupstream side, the valve located within the exhaust gas heat recoveryline being positioned upstream of the EGR cooler.
 9. The exhaust systemof claim 1, wherein the exhaust gas heat recovery line is positionednear an exhaust manifold and parallel to an exhaust passage.
 10. Amethod for heating engine coolant during engine warm-up, comprising:transferring heat from an exhaust flow to the engine coolant via a heatexchanger positioned in an exhaust gas heat recovery line responsive toan EGR valve position, the EGR valve positioned in an exhaust gas linecoupled to the exhaust gas heat recovery line.
 11. The method of claim10, wherein the EGR valve positioned in the exhaust gas line iscontinuously variable and determines a rate of exhaust flow to theexhaust gas heat recovery line, the exhaust flow rate being used tocontrol an amount of heat transferred to the engine coolant based onengine conditions.
 12. The method of claim 11, wherein opening the EGRvalve increases a rate of EGR flow to the engine in the exhaust gasline, the increased flow rate to the engine decreasing a rate of flow tothe exhaust gas heat recovery line.
 13. The method of claim 12, whereinan EGHR valve coupled to the exhaust gas heat recovery line is includedto control the flow rate therethrough, the EGR valve and EGHR valvesbeing adjustable to control the rate of exhaust flow to the exhaust gasheat recovery line to control heat transferred to the engine coolant.14. The method of claim 13, wherein the heat transferred to the enginecoolant is increased for one or more of increasing the rate of heatingin a vehicle cabin and lowering an oil viscosity to enhance an engineoperating efficiency.
 15. The method of claim 14, wherein the rate offlow to the exhaust gas heat recovery line occurs independently of EGRoperation when the EGR valve is closed.
 16. The method of claim 15,wherein closing an exhaust throttle placed in an exhaust passage furtherincreases a rate of flow to one or more of the engine and the exhaustgas heat recovery line.
 17. The method of claim 16, further comprisingshutting the engine off responsive to one or more of a cabin airtemperature in excess of a temperature threshold, the cabin airtemperature being adjusted responsive to heat transferred to the enginecoolant, and a heater control command.
 18. A method for a devicecomprising an EGR cooler coupled to an exhaust gas heat recovery line,comprising: actuating an EGR valve downstream of the EGR cooler toadjust a flow of exhaust gas to an engine intake and a flow of exhaustgas to the exhaust gas heat recovery line, and controlling an amount ofheat transferred from the flow of exhaust gas distributed to the exhaustgas heat recovery line to an engine coolant via a heat exchanger. 19.The method of claim 18, further comprising opening the EGR valvepositioned downstream of the EGR cooler to increase the flow of exhaustgas to the engine intake while decreasing the flow of exhaust gas to theexhaust gas heat recovery line, wherein closing the EGR valve increasesthe flow of exhaust gas to the exhaust gas heat recovery line whiledecreasing the flow of exhaust gas to the engine intake.
 20. The methodof claim 19, further comprising controlling a flow of exhaust gas to theEGR cooler by actuating an exhaust throttle in an exhaust passage.